Reciprocal Superluminal Separation in a Six-Train Control Thought Experiment: A Challenge to the Physical Reality of Kinematic Length Contraction and Time Dilation

Einstein builds the relativity of simultaneity on a single train and a single embankment. I extend his example into a control thought experiment with six trains and three mutually perpendicular embankments, nine inertial frames in all. Two trains, A and B, run in opposite directions beside embankment X, each at 0.99c. Lightning strikes and mirror reflections, timed by simple clocks on the embankment, show that points on A and B move apart by 1.98 light-seconds in every second. I argue that this separation, which each train can attribute to the other with equal right, amounts to a relative speed of nearly twice the speed of light, and that the velocity-composition law used to deny it rests on the very postulates under test. I further argue that special relativity assigns contraction and dilation to the unaccelerated embankment from the standpoint of each train, and to each train from the standpoint of the embankment, and that these mutual assignments cannot all describe physical reality at once. A single spatial segment that serves as the length of one train and the width of another sharpens the difficulty. I conclude that kinematic length contraction and kinematic time dilation do not describe physical changes in bodies or clocks, while gravitational time dilation remains a real effect, and I propose that the question deserves renewed experimental and conceptual scrutiny.